Influences of local polymer–solvent π–π-interaction on dynamics of phenyl ring rotation and its role on photophysics of conjugated polymer

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• 作者：Rakchart Traiphol ; Toemsak Srikhirin ; Teerakiat Kerdcharoen ; Tanakorn Osotchan ; Nico Scharnagl ; Regine Willumeit
• 关键词：MEH-PPV ; Intrachain dynamics ; Conjugation length ; Rotamers ; NMR
• 刊名：European Polymer Journal
• 出版年：2007
• 出版时间：February 2007
• 年：2007
• 卷：43
• 期：2
• 页码：478-487
• 全文大小：1050 K

文摘

In this report, the role of local polymer–solvent π–π-interaction on rotational dynamics of phenyl rings of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is examined by utilizing nuclear magnetic resonance (NMR) spectroscopy. We have found that an aromatic solvent can couple strongly with the phenyl rings via favorable local π–π-interaction, causing a restriction of the ring rotation. The dynamic process takes place at much faster rate in a non-aromatic solvent. NMR line shape analysis indicates the existence of two side chain configurations with relatively long life-time in toluene and pyridine while a single time-averaged configuration is detected in chloroform and tetrahydrofuran. Addition of chloroform or cyclohexane to a solution of MEH-PPV in toluene is accompanied by an increase of the rotational dynamics. This indicates that the expansion or collapse of main chain upon varying solvent quality play a minor role on the rotational dynamics. The relationship between the dynamics of ring rotation and photophysics of MEH-PPV in solution is discussed.